The long term objective of the proposed work is to provide physicians and others in the field of preventive health care delivery with an inexpensive and reliable biochemical test to measure patients' exposure to tobacco smoke products. At present, a reliable test of this type is not available on a commercial basis. We have selected cotinine ( a metabolite of nicotine) as the product to measure, because of its chemical stability, specificity as a marker, and relatively long circulating half-life. Having access to this test will enhance the process of smoking abatement, whether gradual reduction techniques (e.g. nicotine fading) or abrupt withdrawal are employed, and the test can also be employed to emphasize to patients that tobacco smoke products are actually being absorbed into the system. As a first step, an enzyme-linked immunosorbent (ELISA) will be developed for measuring cotinine in saliva and/or urine, capable of assessing qualitatively the extent of tobacco smoke exposure. We intend to take advantage of a recent advance in producing polyclonal cotinine antisera that allows for selective removal of "bridge" antibodies which have, in the past produced high backgrounds and diminished sensitivity. To achieve a detection limit of 10 ng/mL, the cotinine level that separates smokers from non-smokers, we propose to use a simultaneous solid-phase competitive inhibition assay in which binding of enzyme-labeled cotinine antibody to immobilized cotinine is competitively inhibited by cotinine present in the patient sample. In Phase II, we propose to carry out a field trial in physician offices aimed at pregnant women who smoke to test the reliability and efficacy of the product.